Another collision in orbital space has destroyed an operational communications satellite (one of the Iridium birds, which supplies satellite phone service), at an altitude of about 770 kilometers over central Russia. The Iridium satellite was hit, on February 10th, by a dead Russian communications satellite (the one ton Cosmos 2251, equipped with a nuclear power supply, launched in 1993). The Russian bird could not be moved, nor could the Iridium (which, while active, was not equipped with thrusters for movement). The Iridium bird was one of sixty, so satellite phone services was not interrupted, because of the spare capacity in the system. The collision turned the two satellites into 600 bits of debris.
The last time anything like this happened was in 1991, when a dead satellite ran into debris from another, and created more debris. There have been two deliberate collisions since then. Two years ago, China launched a "killsat" that maneuvered into the path of a dead Chinese weather satellite, and destroyed it. Last year, the U.S. Navy used one of its Aegis equipped warships to destroy a malfunctioning U.S. spy satellite with an anti-missile missile. Russia and China have since called for such U.S. activity to be outlawed.
After sixty years of humans putting objects into orbit, there is a lot of junk up there. Currently, over 300,000 dangerous objects 10 mm (.4 inch) in size have been identified. The smallest of these is capable of disabling a satellite, or damaging a spacecraft. That's because these objects hit at very high speed (9-10 times faster than a bullet) if they, and their target, are coming from different directions.
There are nearly 18,000 objects 10 centimeters (4 inches) or larger. These can do some catastrophic damage, to satellites or spacecraft. There are billions of objects smaller than 10mm, and these are responsible for many satellites failing early because of cumulative damage from getting hit by several of these micro objects. There are also about 220 commercial satellites up there, plus nearly as many military ones.
There are lots of people keeping an eye on this clutter. The U.S. Air Force Space Surveillance Network, which tracks nearly 18,000 objects 10mm and larger, stopped sharing all of its information five years ago, for national security reasons. The Russian Space Surveillance System is known to use radar to track over 5,000 objects in low orbit. But the Russians have never shared this data completely, or regularly. Filling in the gaps are two international organizations; IADC (Inter-Agency Space Debris Coordination Committee) and ISON (International Space Observation Network). IADC is a government operation, whose members include the U.S. NASA, and the equivalents in Russia, China and several other major nations. Like most government organizations, not all data is shared.
ISON is a non-government organization, and they come up with some of the most interesting stuff. ISON comprises 18 scientific institutions, 18 observatories, 25 telescopes and over a hundred professionals. ISON does not, as far as anyone knows, withhold data because of any national security concerns. This is fairly certain because ISON work is monitored, and complemented, by the efforts of thousands of amateur astronomers and orbital addicts who connect via the Internet, and constantly scour the orbital space for new objects, and dangerous movements by existing ones.
ISON already has spotted 152 larger (over 10mm) objects that have never been reported by any of the government organizations. The Internet based amateurs are often the first to spot a lot of this new activity, mainly because they have more eyeballs, and, in some cases, impressive optical equipment, searching the skies.
When someone spots an object headed for a maneuverable satellite, the owner is alerted, and the bird is moved. This has happened several times in the last few years. The number of dangerous objects up there increases 10-20 percent a year. That's even with many of them falling into the atmosphere and burning up each year. Apparently, no one was able to predict the collision between Cosmos 2251 and the Iridium bird, largely because the high speed of these objects, and slight instability of their orbits, can turn an expected near miss into a direct hit.